Previous studies by the investigators on a large group of subjects with anxiety neurosis (panic disorder) in Iowa have demonstrated that the disorder is strongly familial with a 41% lifetime morbidity risk among first-degree relatives of affected subjects. Since preliminary genetic analysis indicates that the segregation patterns within families are quite consistent with a single autosomal gene hypothesis, this material provides a unique opportunity to study linkage in a group of families which have cooperated with us in medical research already, in which a pilot linkage investigation has demonstrated feasibility, and in which multiple secondary cases have already been identified among the relatives. Twenty-five kindreds in eastern Iowa with at least one affected relative will be selected from the family study material for linkage analysis. An estimated 12 relatives, including first-, second- and third-degree relatives will be studied. The subjects will receive a structured psychiatric interview by a trained research assistant and psychiatric diagnoses will be made blindly by two experienced psychiatrists. Samples of blood, saliva, and urine will be analyzed for 35 genetic markers. The results will be analyzed for genetic linkage between panic disorder and each of the markers. A segregation analysis on these extended kindreds will be a byproduct of the linkage analysis. A positive finding would indicate that a single gene is important in transmitting the predisposition to panic disorder and would explain why the illness is so strongly familial.